<style>
  .default {
    font-size: 16px;
  }
  .big {
    font-size: 24px;
  }
  .small {
    font-size: 80%;
  }
  .larger {
    font-size: larger;
  }
</style>

<p class="default">hello world</p>
<p class="big">hello world</p>
<p class="small">hello world</p>
<p class="larger">hello world</p>
